The present invention relates to a method and materials for forming a mark such as a product number or a lot number on glass or on-a laser transmittive body used as a component of a liquid crystal panel, a plasma display panel or a semiconductor substrate or the like.
Methods of marking on a transparent body such as glass or a laser transmittive body have been disclosed in Japanese Patent Laid-open No. 008634/1994 and Japanese Patent Laid-open No. 155920/1994.
FIG. 16 and FIG. 17 show the prior art disclosed in Japanese Patent Laid-open No. 008634/1994. In FIG. 16, the numeral 31 represents a glass plate, 32 a metal plate made of material such as stainless steel, phosphor bronze or aluminum, 33 a condensing lens, and 34a and 34b are x-axis and y-axis rotation mirrors for scanning the laser beam LA, and 35a and 35b are galvanometer scanners of x-axis and y-axis rotation mirrors, respectively. According to the marking method of the prior art, the glass plate 31 and the metal plate 32 are closely contacted with each other, a laser beam is applied through the glass to the surface of metal plate 32, a desired pattern such as of a character, a diagram or a symbol, is formed with the heated metal of metal plate 32 by the laser beam irradiation is deposited to the glass plate. By applying the laser beam LA as shown in FIG. 17(a) and separating glass plate 31 from metal plate 32 as shown in FIG. 17(b), metal particles MR deposited to the surface of glass plate 31a is obtained showing the marking of the pattern having the metal color of metal plate 32.
FIG. 18 shows the prior art disclosed in Japanese Patent Laid-open No. 155920/1994. This conventional example uses the same apparatus as shown in FIG. 16, and as shown in FIG. 18, chips 36a and 36b of a thickness of 0.2 to 0.5 mm are placed between glass plate 31 and metal plate 32 to form a gap therebetween. Then a laser beam is applied with a desired pattern such as of a character, a diagram or a symbol through the glass plate to the surface of metal plate 32 to locally heat the surface of metal plate 32a irradiated by the laser beam, thereby emitting matter such as metal particles MR, ions or plasma from metal plate 32 in the direction of the arrow A. As shown in FIG. 18, a part of the matter emitted strikes the surface of confronting glass plate 31, thereby removing surface 31a of glass plate 31 by the shock while forming dent 31b. When glass plate 31 is separated from metal plate 32, dent 31b appears to be white or milky white. Therefore, when the laser beam is applied with a desired pattern while scanning, white marks are formed showing the pattern on the surface of glass plate 31. As described above, there have been two methods for marking on a transparent body such as a glass plate.
However, in the prior art disclosed in Japanese Patent Laid-open No. 008634/1994, since the evaporation area of the metal spreads wider than the diameter of the laser beam, when the laser beam is applied to the metal, it is unable to form minute marks. Further, when a laser beam is applied to metal, since the temperature of the metal is raised as high as the fusion temperature and the metal is closely contacted with the glass surface, the temperature of the closely contacted glass plate is also highly raised locally. Consequently, a crack is occasionally generated in the glass plate which is weaker than the metal plate in thermal shock, or at the worst, the glass plate is broken.
On the other hand, in the prior art disclosed in Japanese Patent Laid-open No. 155920/1994, there is a gap of 0.2 to 0.5 mm between the glass plate to be marked and the metal plate, and since matter such as metal particles MR, ions or plasma generated by irradiation of the laser beam and spread into a two dimensional area, it is not possible been unable to form delicate marking. Further, since the mark is white or milky white in color, it is hard to recognize visually, and with an instrument having a photodetector such as a bar-code reader, it is completely impossible to recognize the marked codes or characters. Further, since a dent is formed in the surface of the glass plate, the bending strength of the glass decreases remarkably. Particularly, in the case of thin glass plate of the thickness of 1 mm or less used as liquid crystal panels, the glass plate is sometimes broken by the bending stress due to dead weight, while precludes mechanical transportation.
Recently, forming marks on a liquid crystal panel or a plasma display panel has been not only for forming product numbers, but also for forming QR Code, Data Code, Veri Code or two-dimensional bar codes or bar codes on a glass plate in the initial process of manufacture for process control of each panel substrate. Therefore, it is greatly required that the mark is of easy recognition, uniform quality, stable and unchanging in quality during manufacture, and low cost.
However, with a marking material of the prior art, the mark such as symbol etc. disappears due to heat treatment in the manufacturing process, and it is difficult to form a predetermined configuration in some marking material, both of which result in increased costs.
Also, in the methods of the prior art, there are problems such as uneveness of thickness of the film on which the mark is formed on a glass plate, part of a mark disappears, and at worst the code can not be read with a data code reader. This is because the film of the code mark is required to shield light completely for reading a code with a code reader, but if there is irregularity in film thickness, the quantity of light shielded by the film of the mark varies, and correct reading of the mark is interrupted thereby.
It is an object of the present invention to provide a method of marking for easily and uniformly forming a minute mark, which has not been realized by the prior art, on a transparent body such as glass or a laser transmittive body. Such a marking method is required to obtain easy visual recognition and instrument reading of a mark, while supplying a marked plate with high strength against bending and which does not cause to crack or fracture from the thermal shock given to the glass plate.
The present invention also provides a marking material for a heat-and-chemicals-proof code mark.
The present invention achieves the above stated object by providing a method for marking materials using a material to be marked and a marking material consisting of a transparent body or a laser transmittive body, comprising a first process of placing the surface of said material to be marked and the surface of said marking material together with a desired gap therebetween, vaporizing said marking material by irradiating it through said material to be marked with a beam of a first laser power while scanning with the laser beam, and depositing a deposit vaporized from said marking material to a predetermined portion of said material to be marked and
a second process of removing or denaturalizing said deposit deposited to the surface of said material to be marked with a laser beam of a second laser power, whereby,
patterns of characters, diagrams or symbols are formed on said material to be marked.
The present invention further provides a method for marking materials to form patterns of characters, diagrams or symbols on a material to be marked consisting of a transparent body or a laser transmittive body comprising the steps of creating a desired gap between the surface of said material to be marked and the marking material,
reacting the gas which exists in said gap from the vaporization of said marking material irradiated by said laser beam with the vaporized marking material, and adhering the reaction product onto the surface of said material to be marked.
In addition, the present invention provides a method for marking materials comprising steps of
forming patterns of characters, diagrams or symbols by changing the light transmittivity or the light reflection factor of the deposit consisting of the marking material deposited to the transparent body or laser transmittive body by irradiating with a laser beam.
A metal, an alloy, an intermetallic compound or a metal compound, or a compound which includes at least one of said metal, alloy, intermetallic compound or metal compound, and in particular a steel or stainless steel is used as the marking material.
According to the present invention, since marking is done by adhering a film onto a glass plate in a first process and partially removing the film in a second process, clear fine marks can be obtained effectively. Also, since the glass plate is not damaged, the glass plate does not break and moreover, a mark with a high bending strength can be effectively provided.
Since the present invention employs stainless steel or steel as a marking material, a heat-and-chemicals-proof code mark can be formed, thereby assuring reliable code recognition on the production line.
Also, as thin film is used on the marking material comprising of a laser transmittive body like a glass plate, a code mark can be formed having a uniform film thickness, making stable code recognition possible.